Push-button with multiple electroconductive contacts returned to rest position by a magnetic device

ABSTRACT

A push-button movable in a casing between two positions corresponding to two switching states of an electric circuit, the casing comprising an insulating plate provided with contact means, some of which are moved by the push-button which is provided with magnetic return means.

United States Patent [1 1 [111 3,906,417

Serras-Paulet 1 Sept. 16, 1975 [54] PUSH-BUTTON WITH MULTIPLE [56] References Cited ELECTROCONDUCTIVE CONTACTS UNITED STATES PATENTS RETURNED To REST POSITION BY A 2,847,528 8/1958 Combs 200/67 F MAGNETIC DEVICE 3,185,803 5/1965 Dn'scoll...

3,283,274 11/1966 DeFalco [75] Inventor ii ;sj;f z gz g gizg 3,448,419 6/1969 Myatt 3,644,856 2/1972 Scott 335/207 [73] Assignee: Neophone Equipment, Paris, France J 10, ExaminerR Envall, Jr.

Attorney, Agent, or FzrmWaters, Schwartz & Nissen [21] App]. No.: 432,336

[57] ABSTRACT {[30] Fore'gn Apphcanon Pnonty Dam A push-button movable in a casing between two posi- Jan. 12, France ti n orre onding to two witching tates of an electric circuit, the casing comprising an insulating plate [52] US. Cl 335/205 provided with Contact means, some of which are [51] Int. Cl. HOIH 36/00 moved b the push-button which is provided with [58] Field of Search 335/205, 206, 207; magnetic return means 200/159 R, 159 A, 67 F 10 Claims, 2 Drawing Figures BEE PUSH-BUTTON WITH MULTIPLE ELECTROCONDUCTIVE CONTACTS RETURNED TO REST POSITION BY A MAGNETIC DEVICE The present invention relates essentially to a pushbutton with multiple electroconductive contacts which are returned to rest position by a magnetic device, forming a control device for the switching of at least one electric circuit and more particularly intended for the making of alphanumeric keyboards usable as data input means.

The push-buttons used at the present time are of two main types. The first type is a push-button returned by a spring, wherein a rigid movable part converts into motion an applied force and transmits this motion to a system of conventional electric contacts, and during this motion a deformable member or spring of predetermined elasticity is compressed so as to return the movable part to its rest position when the external force is no longer applied. The second type comprises push-buttons in which a plastic membrane possessing electrical conductivity constitutes at the same time the said movable contact, movable part and spring, and, under the action of an external force, is applied on flat stationary contacts between which the said membrane forms an electroconductive connection, and then, when the external force is no longer applied, recovers by itself its initial shape, thus interrupting the said electrical connection.

The drawbacks of the said are well known:

In the first type, the reliability of the apparatus is limited by the fatigue phenomena which appear at the return spring subsequent to a variable number of switchings (loss of stiffness, marked subsidence or even downright rupture), and also under the action of corrosion on the said return spring, leading to the same effects.

In the second type of push-button known at the present time, the quality of the electrical connection formed is questionable and uncertain, and it is closely related to the magnitude of the force applied. Furthermore, the quality of the insulation of the push-button in rest position completely depends upon the hazard of an alteration of the mechanical properties of the membrane, owing to the small amplitude of displacement of the membrane in this second type of push-button.

In addition, such push-buttons are particularly sensitive to the technical and climatic environment.

There are also known push-buttons in which a plunger member carrying a magnet is displaced by the action of an external force within a casing comprising a plate of magnetic material. The magnetic attraction between the plate and the magnet returns the plunger member to rest position, but the return force obtained is hazardous and often insufficient owing to the magnet having to lift by magnetic attraction its own weight and that of the plunger member.

The purpose of the invention is to avoid the multiple drawbacks of the push-buttons known in the art at the present time.

To this end, the invention provides a control device for the switching of at least one electric circuit, comprising a casing, 21 push-button movable by pressure exerted on its external end through an opening in a panel of the casing between two positions corresponding respectively to two distinct switching states of the electric circuit, and magnetic means ensuring the return of the two types of push-buttons said push-button and located in the said casing, characterized in that the casing face opposed to the said opening is constituted by a plate of insulating material attached thereto and provided with connecting terminals, contact elements and contact reeds, some of which are movable and driven in motion by the said button, and the latter is provided in its portion within the said casing with a plate or ring of magnetic material cooperating with a permanent magnet solid with the casing to form the said magnetic return means, the maximum air gap between the said permanent magnet and the said plate of magnetic material being equal to the distance between the aforesaid two switching positions of the said push-button.

The switching control device according to the invention therefore enables connections to be formed directly between multiple electroconductive contacts by simply pushing in a push-button, the latter being returned to its rest position by a magnetomotive force which, by its very principle, is not liable to reduction of amplitude as a result of fatigue or by the action of corrosion.

According to another feature of the invention, in both the aforementioned positions corresponding to two distinct switching states of the electric circuit, the push-button bears upon a corresponding abutment, one of the said positions corresponding to a null air-gap of the magnetic return means, the other position corresponding to the aforesaid maximum air gap.

The connections between the multiple electroconductive contacts are thus set up with constant bearing pressures on the contacts, owing to the fact that, in both cases, there takes place a mechanical abutment of the push-button. The effect of this constant bearing pressure on the contacts ensures a constant contact quality.

The invention will be better understood and other purposes, features, details and advantages thereof will appear as the following explanatory description proceeds with reference to the appended diagrammatic drawings given solely by way of example illustrating two forms of embodiment of the invention and wherein:

FIG. 1 shows two longitudinal sectional half-views of the control device according to the invention, one of the said half-views showing the push-button in rest position and the other in pushed-in position; and

FIG. 2 shows two sectional half-views of a modified form of embodiment of the control device according to the invention, one of the said half-views showing the push-button in rest position and the other showing the push-button in pushed-in position.

The switching control device shown in FIG. 1 comprises a hollow casing 1 generally cylindrical in shape, within which a push-button 2 is mounted movably. The lower face of the casing l is closed by a plate 3 of insulating material which is fitted in a groove or slot 4 of the internal surface of easing l. The casing 1 at its opposite end is provided with an internal shoulder 5 cooperating with a shoulder 6 of the external surface of the lower end of the push-button 2 and therefore retaining the push-button within the casing. The upper end of the push-button 2 is provided with a cap of cover 7 which is for example tightly fitted in a central cylindrical orifree 8 of the push-button 2 and substantially covers the upper end of the casing l.

The lower surface of the shoulder 5 carries a perma nent magnet which is annular in shape and defines a central orifice identical with that of the upper portion of the casing 1 and through which passes the body of the push-button 2. A ring 11 of thin magnetic material having an annular shape identical with that of the magnet 10 is secured on the upper face of the shoulder 6 of the push-button 2 so as to be located opposite the permanent magnet 10.

The plate 3 of insulating material is provided on its external face with connecting terminals 13 which are connected with contact elements 14 provided on the internal face of the plate 3. Contact elements 15 may also be connected to some of the connecting terminals 13 and are located within the casing 1 at a distance, from the internal face of the plate 3, corresponding to the maximum air-gap between the magnet 10 and the ring 11 of magnetic material.

The lower portion of the push-button 2, which is permanently located within the casing 1, is formed by a cylindrical surface 17, the diameter of which is much smaller than the internal diameter of the casing and which is provided in proximity to its end with a circular slot 18 in which are inserted the free ends of contact reeds 19 whose other end is secured on the internal face of the plate 3 to the contact elements 14. The contact reeds 19 are elastically deformable and each provided with a contact element 21 which is movable by pressing and releasing the push-button 2 between a contact element 14 secured on the plate 3 and a said contact element 15, if any, located at a distance from the said plate. In the latter case, a reversing switch is obtained.

It will also be noted that the plate 3 of insulating material may be coated on at least one of its faces with a printed electric circuit making certain connections between the connecting terminals 13.

The operation of the device just described is as follows:

In its normal position of rest, the push-button is in the position shown in the lefthand half-view of FIG. 1, wherein the ring 11 of magnetic material attracted by the magnet 10 abuts against the latter and an electrical connection is set up between at least one contact element 21 carried by a reed l9 and a contact element 15 located at a distance from the plate 3. When a force F is applied on the cap 7 of the push-button, the latter moves down into the casing until the cylindrical surface 17 of the push-button abuts against the plate 3 of insulating material. This position is shown in the right-hand half-view of FIG. 1, wherein an electrical connection is set up between at least one Contact element 21 carried by a reed 19 and a contact element 14 carried by the internal face of the plate 3. When the force F ceases to be exerted on the cap 7 of the push-button, the permanent magnet 10 returns the push-button to its rest position by magnetically attracting the said ring 1 1. In both said positions, a constant contact pressure is set up owing to the push-button mechanically abutting against either the plate 3 or the magnet 10.

In a modified form of embodiment, the ring 11 of magnetic material may be constituted by a permanent magnetnhe poles of which are opposed to those of the permanent magnet 10 so as to produce a magnetic attraction force between the two magnets to return the push-button to its rest position. It is possible, in this case, to increase the maximum air-gap between the two magnets, which corresponds to the displacement of the push-button. In order to facilitate the return of the push-button 2 to its rest position, it may be made hollow in order to reduce its weight.

Another form of embodiment is illustrated in FIG. 2, in which the internal face of the plate 3 of insulating material is solid with an annular permanent magnet 25, whereas the lower portion of the push-button 26 is solid with another permanent magnet 27 of the same shape as the magnet 25 and whose poles are arranged opposite the identical poles of the magnet 25 so as to produce between the two magnets a magnetic repulsion force. As previously, an external force exerted on the cap 28 of the push-button 26 moves the push-button into abutment against the plate 3 and the magnet 25 and 27 into contact with one another. When the pressure exerted on the cap 28 is released, the magnetic repulsion force between the two magnets returns the push-button 26 to its rest position shown in the righthand half-view of FIG. 2. In this position, the pushbutton 26 is retained abutting against the shoulder 5 of the casing 1 by the magnetic repulsion between the two magnets 25 and 27. In this case, use is preferably made of high-coercivity magnetic materials.

Therefore, one of the major advantages of the switching control device according to the invention is that the electrical connection between the contact is set up in both positions of the push-button, solely by the action of an external force applied on the end of the pushbutton and by a magnetic attraction or repulsion return-force. The device is therefore highly reliable.

Of course, the invention is by no means limited to the forms of embodiment described and illustrated which have been given by way of example only. In particular it comprises all the means constituting technical equivalents to the means described as well as their combinations, should the latter be carried out according to the spirit of the invention.

What is claimed is:

1. Control device for the switching of at least one electric circuit, comprising a casing provided with a plurality of stationary connecting terminals, stationary and movable contact elements and contact reeds, a push-button which is movable by pressing its external end through an opening of a panel of the casing between abutments of the casing defining two positions corresponding respectively to two distinct switching states of the said electric circuit, said movable contact elements and contact reeds adapted to be moved by said push-button, the said casing being closed at its end opposite to the said opening by a detachably fastened plate of insulating material, said plurality of stationary connecting terminals, stationary and movable contact elements and contact reeds being all mounted on said plate and supported thereby, said contact reeds being further drivingly secured to the said push-button, the latter being provided in its portion located within the said casing with a ring of magnetic material cooperating with at least one permanent magnet solid with the said casing to form magnetic return means acting upon said push-button, the maximum air-gap between the said permanent magnet and the said ring of magnetic material being equal to the distance between the said two switching positions of the said push-button.

2. Device according to claim 1, wherein at least one of the faces of the said plate is coated with a printed electric circuit.

3. Device according to claim 1, wherein the said plate is fitted in a slot of the internal surface of the side walls of the casing.

4. Device according to claim 1, wherein the external surface of the said push-button is provided, in proximity to its end opposed to the said external end, with a slot in which is inserted the free end of each said contact reed.

5. Device according to claim 4, wherein at least some of the said contact reeds are curved to form U-shaped reeds and have their other end secured to the said plate and connected to a connecting terminal.

6. Device according to claim 1, forming also a reversing switch, wherein at least one of the said movable reeds is driven by the push-button between two contact elements, one of which is located on the said plate whereas the other is at a distance from the said plate and is carried by one end of a rigid contact reed whose other end is secured to the said plate and is connected to a connecting terminal.

7. Device according to claim 1, wherein the said permanent magnet is secured to the internal face of the said panel of the casing and is in the shape of a ring surrounding the said orifice of the panel, the said ring of magnetic material having a corresponding shape and being secured to a shoulder of the said push-button.

8. Device according to claim 1, wherein the said ring of magnetic material carried by the push-button is constituted by a second permanent magnet.

9. Device according to claim 8, wherein the first and second permanent magnets are so arranged as to have their opposed poles in mutually confronting relationship.

10. Device according to claim 8, wherein the said first and second permanent magnets are so arranged as to have their identical poles arranged in mutually confronting relationship, respectively, whereby the return means act upon the push-button by way of magnetic repulsion, and the said first permanent magnet is secured to and solid with the casing in such a position, with respect to the second permanent magnet solid with the push-button, that the axial air-gap between the magnets is annulled when the button is moved from its rest position to its other position by pressing its external end. 

1. Control device for the switching of at least one electric circuit, comprising a casing provided with a plurality of stationary connecting terminals, stationary and movable contact elements and contact reeds, a push-button which is movable by pressing its external end through an opening of a panel of the casing between abutments of the casing defining two positions corresponding respectively to two distinct switching states of the said electric circuit, said movable contact elements and contact reeds adapted to be moved by said push-button, the said casing being closed at its end opposite to the said opening by a detachably fastened plate of insulating material, said plurality of stationary connecting terminals, stationary and movable contact elements and contact reeds being all mounted on said plate and supported thereby, said contact reeds being further drivingly secured to the said push-button, the latter being provided in its portion located within the said casing with a ring of magnetic material cooperating with at least one permanent magnet solid with the said casing to form magnetic return means acting upon said push-button, the maximum air-gap between the said permanent magnet and the said ring of magnetic material being equal to the distance between the said two switching positions of the said push-button.
 2. Device according to claim 1, wherein at least one of the faces of the said plate is coated with a printed electric circuit.
 3. Device according to claim 1, wherein the said plate is fitted in a slot of the internal surface of the side walls of the casing.
 4. Device according to claim 1, wherein the external surface of the said push-button is provided, in proximity to its end opposed to the said external end, with a slot in which is inserted the free end of each said contact reed.
 5. Device according to claim 4, wherein at least some of the said contact reeds are curved to form U-shaped reeds and have their other end secured to the said plate and connected to a connecting terminal.
 6. Device according to claim 1, forming also a reversing switch, wherein at least one of the said movable reeds is driven by the push-button between two contact elements, one of which is located on the said plate whereas the other is at a distance from the said plate and is carried by one end of a rigid contact reed whose other end is secured to the said plate and is connected to a connecting terminal.
 7. Device according to claim 1, wherein the said permanent magnet is secured to the internal face of the said panel of the casing and is in the shape of a ring surrounding the said orifice of the panel, the said ring of magnetic material having a corresponding shape and being secured to a shoulder of the said push-button.
 8. Device according to claim 1, wherein the said ring of magnetic material carried by the push-button is constituted by a second permanent magnet.
 9. Device according to claim 8, wherein the first and second permanent magnets are so arranged as to have their opposed poles in mutUally confronting relationship.
 10. Device according to claim 8, wherein the said first and second permanent magnets are so arranged as to have their identical poles arranged in mutually confronting relationship, respectively, whereby the return means act upon the push-button by way of magnetic repulsion, and the said first permanent magnet is secured to and solid with the casing in such a position, with respect to the second permanent magnet solid with the push-button, that the axial air-gap between the magnets is annulled when the button is moved from its rest position to its other position by pressing its external end. 